At the present time, the problem of extending the processing capacities of vibratory equipment under development is very urgent since it allows reductions in the component machining time and, consequently, in power consumption, which leads to increased productivity per unit time and improved quality of vibration treatment. Unbalance vibrators used most commonly for the generation of disturbing forces are of the mechanical inertia unbalance type which offers simplicity in operation and fairly high disturbing forces. Under operating conditions, a necessity may often arise for the amount of disturbing force generated by the vibratory device to be adjusted over a wide range, for example, in order to adjust the oscillation amplitude in the vibratory device.
The amount of vibrational force generated is directly proportional to the mass of unbalance weight, which is arranged eccentrically with respect to the axis of rotation of the drive shaft, the distance of the centre of this mass from the axis of rotation of the drive shaft, and to the squared frequency of rotation (angular velocity) of the drive shaft.
By virtue of the fact that varying the frequency of rotation of the drive shaft over a wide range necessitates the use of a d.c. motor in conjunction with a supply voltage regulator, the simplest ways of varying the amount of the disturbing force would be either by changing the eccentric mass of the unbalance vibrator or by altering the distance from the centre of its masses to the axis of rotation of the drive shaft.
Known in the present state if the art is an unbalance vibrator comprising a drive shaft which is rotatably mounted in the housing and carries a balanced disk fixed stationary on the shaft and having holes adapted to receive one or several rods to provide for adjustment of the eccentric mass (cf., e.g., a textbook "Mechanisms", in Russian, "Mashinostroyenie" Publishers, Moscow, 1976, p. 669, FIG. 11.4). Such an unbalance vibrator is too complicated in manufacture because of the need to provide reliable clamping of the movable rods in conjunction with their rapid replacement required for changing the amount of the eccentric mass.
Another unbalance vibrator known presently comprises a drive shaft carrying an unbalance weight fixed stationary on the shaft and another unbalance weight which is movable in a circular direction and can be fixed in position on the shaft by means of a key joint and offers a plurality of key slots determining the number of its positions relative to the fixed unbalance weight (cf., e.g., a texbook "Mechanisms", in Russian, "Mashinostroyenie" Publishers, Moscow, 1976, p. 668, FIG. 11.3, b). Turning the movable unbalance weight with respect to the fixed unbalance weight causes displacement of their common mass centre relative to the axis of rotation of the drive shaft and, consequently, a change in the amount of vibrational force which the vibratory device will produce.
A common disadvantage of both of the aforedescribed unbalance vibrators resides in the fact that the produced vibrational force can only be varied within a comparatively narrow range, which restricts the field of application of unbalance vibrators of these types.
The closest to the herein proposed invention is a centrifugal unbalance vibrator (DE, C, 1,297,928) comprising a fixed shaft fitted in a rotary electric motor. Fixed stationary on the housing of the electric motor is an unbalance weight made in the form of an arc-shaped guide supporting another movable unbalance weight made in the form of an arc-shaped element. The unbalance weights are provided with a mechanism for adjusting their mutual position and fashioned as a pin retainer spring-loaded in a radial direction. One end of the retainer projects over the fixed unbalance weight while the other end engages in and is movable within a blind radial hole passing through the fixed unbalance weight and the motor housing. The projecting end of the pin retainer is engageable in one of the through radial holes provided in the movable unbalance weight dependent on the amount of static moment which can be varied by displacing the centre of masses of the movable and the fixed unbalance weights effected through circular movement of the movable unbalance weight. The amount of static moment of the unbalance weights is proportional to the amount of the disturbing force produced. For adjusting the disturbing force, a cylindrical pin or screwdriver is fitted in the hole interacting with the rod end by means of which the retainer end is held in the radial hole, while the unbalance weight is moved to another position corresponding to the angle between two adjacent holes, so that the retainer should engage in one of the adjacent holes in the movable unbalance weight, from which hole it can be disengaged using said pin or screwdriver.
A substantial disadvantage of the prior-art unbalance vibrator mentioned above resides in the fact that the mechanism for adjusting the mutual position of the unbalance weights does not allow the disturbing force to be varied over a wide range, which prevents vibration treatment of a wide range of products. Another disadvantage of the prior-art unbalance vibrator lies with the sophisticated adjustment of the disturbing force, since the adjustment process involves the use of an additional tool such a cylindrical pin or rod, which has to be fitted, in succession, in each of the through holes passing underneath the movable retainer, thus increasing the total adjustment time.
Furthermore, the unbalance vibrator discussed above features a comparatively high drag coefficient because of the clearance between the movable unbalance weight and the motor housing, which increases noise during operation of the unbalance vibrator.